This invention relates to a traveling wave generator and more particularly to such a generator which generates a planar traveling wave in a flexible body such as a robotic fish tail or snake.
Currently robotic fish and snake-like vehicles typically consist of a flexible body surrounding a multitude of rigid links connected in series, much like the spine of the animal that the vehicle emulates. The motion of each link is controlled by at least one dedicated actuator, as it is in the biological model, e.g., U.S. Pat. No. 6,138,604.
This approach requires a large number of actuators that must be coordinated to generate the desired vehicle motion. Such a device requires some form of logic generator such as a microprocessor, as well as a power distribution network to supply the individual actuators with power. Often there is a problem with fitting actuators in the confined spaces of the vehicle, such as at the end of a fish or snake-like tail. These problems result in a costly, and often large, heavy and complicated mechanism that may not perform as desired.
It is therefore an object of this invention to provide an improved traveling wave generator.
It is a further object of this invention to provide such an improved traveling wave generator which is small, compact, light, simple and less costly.
It is a further object of this invention to provide such an improved traveling wave generator which requires only a single motion source and one which can run at constant speed.
It is a further object of this invention to provide such an improved traveling wave generator which can be employed in a fish or snake-like device.
It is a further object of this invention to provide such an improved traveling wave generator which allows for a wide range of resulting wave shape and propagation envelope.
The purpose of the invention is to provide a simple means of generating a planar traveling wave in a flexible body, such as a robotic fish tail or snake. The invention uses a single actuator, or motor, to drive links connected in series that comprise the mechanism, but the invention allows for a greater range in resulting wave shape. The invention is capable of generating a traveling wave in a flexible body such as a fish or snake-like tail using a single actuator, or motor, to drive a multitude of links. The device requires no logic to perform this function. The invention provides a simple, low cost solution to the problem of mechanizing small fish and snake-like robots. The invention consists of a series of rigid links connected in series and hinged such that the assembly can bend in a single plain. The invention must contain at least two links, but there is no theoretical limit to the total number of links in the invention. Traveling down the center of the links may be a rotating shaft, made up of a series of rigid elements connected by universal or constant-velocity joints. The centers of the joints are coincident with the hinge axes between the links. This arrangement allows the shaft to turn freely as the angles between the links are moved through arbitrary small angles. Near the rearward end of each shaft is located an eccentric cam that turns with the shaft and engages a race, or slot, in the end of the next link in the mechanism. As the shaft in the first link revolves, the cam imparts an oscillating motion to the second link. The shaft in the second link imparts an oscillating motion to the third link (if there is one), and so on. The phasing and amplitude of the link motions can be adjusted by the angular and axial position of the eccentric cams on the shafts, respectively. The invention provides a simple, low cost method of actuating a fish or snake-like robotic vehicle, which has formerly required a much more complex and costly mechanism. The invention also provides a means of miniaturizing such robotic vehicles, which would be very difficult using the former methods.
The invention results from the realization that a truly simple and effective traveling wave generator can be made using at least a base link, an end link and an intermediate link pivotably interconnected to oscillate in a plane with a drive mechanism that interconnects each pair of links including a drive shaft and a cam on a first link of the pair and on the second link of the pair a follower for engaging the cam to include a traveling wave motion in the links; a flexible power transmission device interconnects the shafts of each of the base and intermediate links to drive them from a motion source.
This invention features a traveling wave generator including at least a base link, an end link and an intermediate link. A pivot device pivotably interconnects each pair of links. A drive mechanism interconnects each pair of links and includes a drive shaft and a cam on the first link of the pair and on the second link of the pair a follower for engaging the cam for inducing a traveling wave motion in the links. A flexible power transmission device interconnects the shafts of each of the base and intermediate links and a motive source rotates the shafts.
In a preferred embodiment the pivot devices may be in the same plain and the induced traveling wave may be in a single plain. The cam may be spherical or semispherical. The drive mechanism may include an adjustment device for setting the relative phase orientation of the cams on their shafts to define the wavelength of the traveling wave. The drive mechanism may include an adjustment device for setting the position of the cams along their shafts to define the envelope within which the traveling wave propagates. The flexible power transmission device may include a universal joint or may include a constant velocity joint. The axes of the flexible power transmission devices may be aligned with the associated pivot devices in each link. The motive source may drive the shaft of the base link or may drive any one of the other shafts of the interconnected links. The links may have different lengths for defining the envelope within which the traveling wave propagates. The cam may be cylindrical and the follower may be pivotable.